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Use the target-specified iteration count to opt out of any further refinement of an estimate. NFC.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218700 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2014-09-30 20:44:23 +00:00
parent cafc85bf1e
commit 73a335f7f6
1 changed files with 60 additions and 58 deletions
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10
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -11778,8 +11778,9 @@ SDValue DAGCombiner::BuildReciprocalEstimate(SDValue Op) {
// Expose the DAG combiner to the target combiner implementations.
TargetLowering::DAGCombinerInfo DCI(DAG, Level, false, this);
unsigned Iterations;
unsigned Iterations = 0;
if (SDValue Est = TLI.getRecipEstimate(Op, DCI, Iterations)) {
if (Iterations) {
// Newton iteration for a function: F(X) is X_{i+1} = X_i - F(X_i)/F'(X_i)
// For the reciprocal, we need to find the zero of the function:
// F(X) = A X - 1 [which has a zero at X = 1/A]
@ -11806,7 +11807,7 @@ SDValue DAGCombiner::BuildReciprocalEstimate(SDValue Op) {
Est = DAG.getNode(ISD::FADD, DL, VT, Est, NewEst);
AddToWorklist(Est.getNode());
}
}
return Est;
}
@ -11819,8 +11820,9 @@ SDValue DAGCombiner::BuildRsqrtEstimate(SDValue Op) {
// Expose the DAG combiner to the target combiner implementations.
TargetLowering::DAGCombinerInfo DCI(DAG, Level, false, this);
unsigned Iterations;
unsigned Iterations = 0;
if (SDValue Est = TLI.getRsqrtEstimate(Op, DCI, Iterations)) {
if (Iterations) {
// Newton iteration for a function: F(X) is X_{i+1} = X_i - F(X_i)/F'(X_i)
// For the reciprocal sqrt, we need to find the zero of the function:
// F(X) = 1/X^2 - A [which has a zero at X = 1/sqrt(A)]
@ -11855,7 +11857,7 @@ SDValue DAGCombiner::BuildRsqrtEstimate(SDValue Op) {
Est = DAG.getNode(ISD::FMUL, DL, VT, Est, NewEst);
AddToWorklist(Est.getNode());
}
}
return Est;
}